Лимит времени 2000/4000/4000/4000 мс. Лимит памяти 65000/65000/65000/65000 Кб. Question by Ibrahim Mesecan.
Area of an Irregular Polygon
When calculating the area of an irregular polygon,
all the vertices are written down in order ending
with the starting vertex. Then the product of
first y with the second x is subtracted from
the product of first x is with the second y, etc.
Question:
Write a program that calculates the area
of the given polygon.
Input specification
You are given first an integer number n
0 ≤ n ≤ 10,000. Then, in the following n lines
you are given coordinates of an irregular polygon.
Each coordinate x and y can have any value between
-20,000 and +20,000.
Output specification
Show one number with one digit double precision: Area
of the given polygon.
Sample Input
5
-3 -2
-1 4
6 1
3 10
-4 9
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Sample Output
60
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Для отправки решений необходимо выполнить вход.
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